The metabolic syndrome (MetS) is a cluster of factors that increases the risks for cardiovascular disease, type 2 diabetes mellitus, and mortality, and currently affects > 40% of US adults. MetS is associated with endothelial dysfunction, decreased circulating endothelial progenitor cells (EPCs), and a pro-inflammatory state. We have made the exciting discovery that therapy with allogeneic mesenchymal stem cells (MSCs) restores endothelial dysfunction and circulating EPCs towards normal the levels, and reduces markers of inflammation. Endothelial function represents a key driver of cardiovascular morbidity and mortality in MetS, and as such, restoring endothelial function could lead to clinical benefits in this patient population. We will conduct a clinical trial using Longeveron-produced allogeneic mesenchymal stem cells (LMSCs) delivered to subjects with MetS. In Phase I of this study, we will perform a dose-escalation Safety Run-In to first establish safety of LMSC therapy in subjects with MetS. After a safety review and approval from an independent data safety monitoring board (DMSB), Phase II of this Fast-Track Study will commence. This will entail a Randomized, Double-Blinded, Placebo-Controlled Phase on 40 subjects with MetS. The following specific aims will be examined. Specific Aim #1: To test the hypothesis that LMSCs are safe to intravenously-administer to subjects with MetS. We will examine for incidence of treatment-emergent serious adverse events (TE-SAEs); blood chemistry, hematology, coagulation, and urinalysis; and alloimmune reaction and T and B cell subsets to examine levels of immune activation. Specific Aim #2: To test the hypothesis that intravenously-administered LMSCs will improve endothelial dysfunction and increase circulating EPCs in subjects with MetS. We will examine endothelial dysfunction using flow-mediated vasodilation (FMD), and circulating EPCs by colony assays and flow cytometry. Specific Aim #3: To test the hypothesis that intravenously-administered LMSCs will improve systemic markers of inflammation in subjects with MetS. We will use ELISA to examine panels of inflammatory markers. Specific Aim #4: To test the hypothesis that intravenously-administered LMSCs will lead to clinical improvement in subjects with MetS. We will examine for changes in glucose control (hemoglobin A1c, fasting glucose, fasting insulin, HOMA), lipid profile (HDL, LDL, triglycerides, cholesterol), blood pressure and cardiac function, physical performance, and subject quality of life. We anticipate that the results of this study will lead to a much needed therapeutic for subjects with MetS. Longeveron is positioned to rapidly advance this program to a pivotal phase III trial if the results prove positive, and to bring this technology to market.